US2144337A - Electrical device - Google Patents

Description

Jan. 17, 1939. W. R KOCH 2,144,337

ELECTRICAL DEVICE AMPLlF/ER Patent Jan, 17, 1939 UNIED YSTATES PATENT OFFICE 2,144,337 ELECTRICAL DEVICE Winiield R. Koch, Camden, N. J., assigner to Radio Corporation of America, a. corporation of Delaware My invention relates to electric wave shaping apparatus and particularly to a method of and means for producing an electric wave of the desired wave shape by deflecting a cathode ray.

Various forms of apparatus have been employed for producing electric waves having a wave shape other than that of a sine wave. Such apparatus generally includes thermionic vacuum tubes, iron core inductances, gas discharge tubes, or the like. It is often diicult to obtain exactly the desired wave shape when employing such apparatus.

An object of my invention is to provide an improved method of and means for producing electric waves of any desired wave shape. A further object of my invention is to provide improved apparatus including a cathode ray tube for producing an electric wave of non-sinusoidal wave form.

In one embodiment of my invention a cathode ray tube is so designed that the cathode ray is spread out in a plane or line instead of being confined to a, ray of small diameter, as is customary in cathode ray tubes. This plane or line of electrons is projected towards a plate having a shape which preferably conforms to the wave shape desired, and the cathode ray is deected along this plate whereby the number of electrons striking the plate varies from instant to instant to produce a ow of current having the said wave shape.

One of several other embodiments of the invention includes a cathode ray tube having a fluorescent screen and further includes a photo-electric cell and a mask positioned between the fluorescent screen and the photo-electric cell. The mask has an opening therein which preferably has a shape which conforms to the wave shape of the desired electric wave whereby the amount of light reaching the photo-electric cell varies from instant to instant as the cathode ray is deflected across the fluorescent screen.

Other objects, features and advantages of the invention will appear from the following description taken in connection with the accompanying drawings, in which y Figures 1, 2 and 3 are schematic and circuit diagrams of three embodiments of my invention,

Figures 4, 5 and 6 are end views oi the mask and cathode ray tube shown in Figure 3, the three different views showing masks with three different lshaped openings,

age of the proper value supplied thereto. If de- Fig. 8 is a block diagram of a radio transmitter utilizing my invention.

' Referring to Fig. 1, the apparatus includes a cathode ray tube comprising an evacuated envelope I, an indirectly heated cathode 2, a control 5 grid 3, a rst anode 4 and a second anode or signal plate 6, which is specially shaped as above mentioned. Preferably another plate I is provided adjacent to the plate 6, as illustrated, for the purpose of aiding in the acceleration of the electrons and for providing a return path for electrons which do not strike the signal plate 6.

A screen grid 8 and a suppressor grid 9 may be provided which serve the same purpose as like grids in conventional amplier tubes. 15

In the embodiment illustrated, the cathode ray is spread out into a plane or line at right angles to the plane of the paper by means of two deflecting or focusing plates I I which have a fixed voltsired, the same results may be accomplished by properly designing the electron gun and omitting the focusing plates.

Suitable positive voltages are supplied to the first anode 4, the grids 8 and 9 and the plates 6 and i from a suitable source such as a battery indicated at I2. A negative biasing voltage is supplied to the control grid 3 from a suitable source such as a battery I3. l

Voltage is supplied to the signal generating plate 6 through an output resistor I4 across which the desired signal voltage appears. This signal voltage may be supplied through a coupling condenser I 6 to a suitable amplifier I1.

The operation of this apparatus depends upon the fact that as the electron stream, indicated at I8 by the dotted lines, is deflected in a vertical plane by suitable deecting devices such as deflecting plates I9, the number of electrons striking the signal plate 6 and passing through the output resistor I4` depends upon the angle of deflection of the electron stream. For example, with the electron stream in the position indicated on the drawings, the amount of current flowing through the output resistor I4 is greater than when the electron stream is deflected further from the center of the tube and it is less than' when the electron stream is deflected towards the center of the tube. Obviously, the current iiow through the output resistor I4 and, therefore, the voltage applied to the grid of the amplifier tube I1 depends upon the shape of the signal plate 6 and the wave shape of the voltage applied to the deiiecting plates I9. The deilecting voltage, preferably, is either sinusoidal or saw-tooth in wave form.

Referringto ,2 of the drawings. there is illustrated a cathode ray tube 2i which'is con-"f ventional in construction except for certain modif yilcations which rwill be, described. The tube includes the usual electron gun 22 and second anode 23, ,thev electron beam being focused electrof statically. As, in ,the embodiment ofthe invention shown in Fig. 1, a signal plate 24 isy provided which is positioned in the path oi' the electron beam yand shaped in accordance with thewave form of the signal wave to be generated. yThe f signal plate 24 is connected through an output resistor 2,6 to ground whereby a ilow of current is produced through the resistor whichfis propor-r tional to the number of electrons striking the This elecelectrons traverse the signal plate 24'along a yliney as indicated by the dotted lines 28. In order to yproduce thedesired 'signal wave, the electron beam is also deflected in a'plane substantially at right angles to the ilrst deflection by means of otherdeflectin plates 23 or other suitable deflecting devices. f f f f f f -It will be understood that the operation is substantially the same as the operationof the device previously described. 'The'mainfdiilerence in operation is that, while the electron beam is being deflected vertically by means of the low frequency deflecting plates 29,y impulses of energy are being applied to the signal plate 24 at the frequency op the deection produced by the other deilecting plates y21.r f 'Because of this, ,ther signal voltage appearing across the resistor 26 is supplied to the amplifier tube l1 through a filter 3| which may consit of an inductance coil 32 and shunt condensers 33 and 34. The filter 3l is given a time constant which is greater than the period of the deilecting .wave applied to the high frequency deflecting plates 21 whereby an uninterrupted voltage is applied to the grid of tube I1, the magnitude cf the voltage changing in consonance with the low frequency deilection of the cathode beam and in accordance with the shape of the signal plate 24.

Deilecting waves of any desired Wave form may be applied to the deilecting plates but in general either sine waves or saw-tooth waves are preferred.

Referring to Fig. 3, the cathode ray tube 36 may be the same as the tube 2| shown in Fig. 2, except that a fluorescent screen 31 is provided at the end of the tube. In this embodiment of the invention, it is desired to produce a line of light on the fluorescent screen and to deflect this line of light behind a mask having an opening therein whereby the amount of light passing through the mask depends upon the shape of the opening. In the drawings, a photo-electric cell is indicated at 38 for receiving light from the uorescent screen 31. A mask 39 and a suitable optical system 4| are located between the photo-electric cell 38 and the screen 31. One form of mask is shown in Fig. 4, this being an end view of the mask 39 and cathode ray tube 36.

In the particular embodiment shown in Figs. 3 and 4, the electron beam is deflected vertically at a comparatively high frequency by deflecting plates 42; whereby,y as the electron beam is deilected more slowly in the horizontal plane by the deilecting plates 43, a vertical line of light moves across themask opening. As the line of light moves from the center of the tube to either side, the amount of light passing through the photo-electric cell 38 increases. be provided in the output circuit of the photof electric ycell y38,fas,indicated, in order to integrate the light impulses caused by the high frequency f f deection ofthe electron beam. It will be understood that the necessary'filter action may be provided in the photo-electric cell amplifier I6 itself, f

if desired. As in the apparatus rshown in Fig. 2, rthe illter'requirements are that the time constant of the filter be greater than the period'of' high frequency deflection.

,By yproperly shaping the opening of the mask, any desired alteration in wave shape can' be secured. Thus, if"square law operation is desired.feach sldeof the openingof the mask 39 is given a parabolic curve as' shown rinr Fig. 4.' With this mask and with a saw-tooth voltage applied to ,theme11 frequency deilecting plates 42 and a sine wave voltage, indicated' at '45 in' Fig. 7, apa

plied to the low frequency deflecting plates 43,

, ,the yresulting signal supplied to the amplifier 46 has the wave shape indicated' by' the'curve 41 in Fig. 7. It will be noted that this signal is sinusy roidal in wave form and has double the frequency of the signal applied to the low'frequeney deilecting plates 43, this being the signal which is re-shaped.

By using a mask "with an opening having the f lating audio wave at a transmitter may be given a square root shape so that with alinear modulator at the transmitter the receiver may have a square law detector without any resulting distortion. With a high frequency saw-tooth wave applied to the plates 42 and with the modulating sine Wave applied to the plates 43, the resulting wave having the square root shape is shown by the curve 50 in Fig. 7.

'I'he diagram in Fig. 8 shows how such a wave shaper may be vincluded in a radio transmitter. A wave shaper of the type above-described is indicated at 43.

By making the opening in a mask 5I of the shape shown in Fig. 6 the cathode ray tube may be employed to give linear detection by applying the radio or intermediate frequency voltages to the deecting plates 43. 'I'he wave form of the signal applied to the ampliiier 46 when the mask is of the form shown in Fig. 6 isindicated by the curve 52 in Fig. 7. It will be apparent that this is a rectified'sine wave. f

It may be noted that if the uorescent material of the fluorescent screen continues to glow after the bombardment stops, the slope of the decay curve should be steep and the shape of the opening in the mask may have to be modified.

From the foregoing description, it will be apparent that various other modifications may be made in my invention without departing from the spirit and scope thereof and I desire, therefore, that only such limitations shall be imposed thereon as are necessitated by the prior art and are set forth in the appended claims.

I claim as my invention:

1. An electrical wave generator comprising an electric discharge tube having means for producing a stream of electrons spread out in a certain yOpeningincreases, whereby the output of the Afilter44'sho'u1dy f plane whereby their cross-section is a line, a iluorescent screen positioned in the path of said electrons whereby a line of light is formed thereon, a photo-electric device positioned to receive said' light, a mask positioned between .said fluorescent screen and said photo-electric device,

said mask having an opening therein which is ,f

shaped in accordance with the desired wave shape of the electrical wave to be generated, and means for defiecting said stream of electrons substantially at right angles to said certain plane whereby the amount of light reaching said photo-electric device from said line of light varies in accordance with the shapey of said mask opening.

2. An electrical wave generator comprising an electric discharge tube having means for producing a beam of electrons, a signal plate of electrically conducting material shaped in accordance with the desired wave shape of the electrical wave to be generated, means for deilecting said electron beam at a comparatively high frequency in a certain plane whereby said electrons strike said signal plate along a line, means for deilecting said electron beam periodically at a comparatively low frequency and substantially at right angles to said line, whereby the number of electrons striking said plate is varied, and means including a illter for taking the resulting signal from said plate, said lter having a time constant which is larger than a period of said high frequency deflection.

3. An electrical wave generator comprising an electric discharge tube having means for producing a beam of electrons, means for deecting said electrons in a certain plane at a comparatively high frequency, a uorescent screen positioned in the path of said electrons whereby a line of light is formed thereon, a photo-electric device positioned to receive said light, a mask positioned between said iiuorescent screen and said photoelectric device, said mask having an opening therein which is shaped in accordance with the desired wave shape of the electrical wave to be generated, means for deiiecting said'beam of electrons substantially at right angles to said certain plane whereby the amount of light reaching said photo-electric device from said line of light varies in accordance with the shape of said mask opening, and an output circuit for said photo-electric device, said output circuit having a time constant which is larger than the period of one of said high frequency oscillations.

4. An electrical wave generator comprising an electric discharge tube having means for producing a beam of electrons, means for deecting said beam in a certain plane at a comparatively high frequency, means including a screen structure so positioned in the path of said beam that said deection causes said beam to trace a line thereon for generating in response to deflection of said beam at right angles to said certain plane a signal voltage having a. wave shape determined i by the outline of said screen structure, means for deecting said beam at right angles to said certain plane at a comparatively low frequency, an output circuit including a filter having a time constant which is larger than the period of one of said high frequency oscillations, and means for supplying said signal voltage to said output circuit.

5. An electrical wave generator comprising an electric discharge tube having means for producing a stream of electrons effectively spread out in a certain plane whereby their effective cross-section is a line, means for deflecting said beam periodically in a plane substantially at right angles to said certain plane in accordance with an electrical field, and means including a screen structure having an area. bounded by an edge parabolic in shape and by an opposite edge which is a straight line for making successively changing fractions of said line of electrons eilective to produce signals during said deflection, said screen structure being located with said straight line edge at right angles to said certain plane whereby the wave shape of said signals is the square root DISCLAIMER -2,l44,337.-Win eld R. Koch, Camden, N. J. ELECTRICAL DEVICE. Patent dated' January 17, 1939. Disclaimer led November 22, 1939, by the asslgnee,

Radio Corporation of America.

Hereby enters this disclaimer to claims 2 and 4 in said specification.

[Qcicl Gazette December 12, 1.939.]

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